1. Technical Field
The present invention relates to a method for heating glass sheets to be tempered or heat-strengthened, in which method glass sheets are heated in a preheating furnace by applying a hot-air blast and convection heating produced thereby to the opposite sides of a glass sheet and the preheated glass sheet is transferred from the preheating furnace into a radiation heating furnace for heating the glass sheet to a tempering temperature.
2. Background Art
In such prior known tempering furnaces, a drawback involved in preheating is that the heating efficiency deteriorates as the glass temperature rises. Thus, the preheating station is not capable of reaching a very high temperature or, alternatively, the heating time increases unacceptably.
In view of the above described deficiencies associated with the use of known methods for heating glass sheets to be tempered or heat-strengthened, the present invention has been developed to alleviate these drawbacks and provide further benefits to the user. These enhancements and benefits are described in greater detail hereinbelow with respect to several alternative embodiments of the present invention.
The present invention in its several disclosed embodiments alleviates the drawbacks described above with respect to conventional methods for heating glass sheets to be tempered or heat-strengthened and incorporates several additionally beneficial features.
An object of the invention is to improve this type of tempering method, such that the preheating can be intensified and expedited even though the air temperature is maintained substantially constant.
This object is achieved on the basis of the characterizing features set forth in the annexed claims 1 and 2.